With more individuals living longer nd retaining their teeth longer, the dental health needs of the "older adult" population (over 64 years old) are changing. With the increase in retained teeth, more root caries are being seen. Other factors, including diseases, medication, and radiation therapy may also be influencing the prevalence of root caries in older persons. The development of materials that adhere to dentin has promised to improve the treatment of root caries. However, evidence suggests that the improvement may be insignificant in older persons. This study will examine the hypothesis that for currently available materials there is an age dependency for dentin bonding. The retention and the quality of dentin-bonded composite resin restorations in older adults and adults age 30 to 50 will be compared. Two populations of human subjects will be used in the clinical portion of the study. A group of 43 "older" adults will be compared to 43 individuals aged 30 to 50 will be compared. Two populations of human subjects will be used in the clinical portion of the study. A group of 43 "older" adults will be compared to 43 individuals aged 30 to 50 years. Restorations will be placed in paired erosion lesions. The only retention will come from the dentin bonding agent. Two different dentin bonding agents will be used to bond the restorations. One is a standard, much evaluated material; the other is a new material which is reported to form very strong bonds with dentin. Evaluations will be made at baseline, 2, 6, nd 12 months. The retention, marginal integrity, anatomic form and color match will be evaluated. Impressions and photographs will be taken at each recall. The laboratory portion of this study will use caries-free extracted molars. Microleakage tests will be conducted using 76 teeth - half from patients each age group. Tests will be conducted using both boding agents. Class V preparations of 4x2x2mm will be made in the buccal and lingual surfaces of each molar. The teeth will be aged seven days then thermocycled. Progress of a dye down restoration margins will be measured. The dye will be used to compare the microleakage of dentin bonded restorations of each type in teeth from "older adults" and "adults". The bonding agent/dentin interface of some of these teeth will be examined by Scanning Electron Microscope. The adaption of the bonding agents to "old adult" and "adult" dentin will be compared in order to learn the microstructural basis for observed differences in performance.